As an apparatus of this type, for example, there is known a camcorder. Such apparatus uses a magnetic tape as a recording medium and adopts a helical-scan mechanism which uses a rotary drum to increase the recording density of the recording medium. In this mechanism, however, noise called head rattle is generated when the magnetic tape comes into contact with or separates from a rotary printhead. Since energization of a magnetic motor coil is switched on/off to drive the rotary drum, electromagnetic noise also occurs. These noise components enter an internal microphone and are recorded together with speech to be recorded, and the speech becomes offensive to the ear.
To solve the problem, there is disclosed a noise reduction method of examining in advance the spectrum of noise which may enter a microphone and subtracting a component in the band in accordance with the magnitude of the noise (e.g., Japanese Patent Laid-Open No. 7-177596).
According to this proposal, a means for extracting a component in the noise spectrum is provided, the level of the noise is measured while speech to be recorded is cut off, and control is performed such that a noise component to be subtracted has the same level as that of the noise mixed with the speech. With this operation, the noise is reduced by the level of the spectrum of the noise and produces little effect on speech when the speech is input.
However, in the conventional methods, noise components need to be examined in advance, and a means for extracting noise by the number of spectral components in the noise, i.e., bandpass filters are necessary. To avoid this, there can be considered a method of collectively extracting frequencies whose spectra are close to each other and reducing the number of bandpass filters. For example, when the noise spectra are 1 kHz and 2 kHz, the center frequency is set to 1.5 kHz, and the bandwidth is set to 1 kHz, noise components of 1 kHz and 2 kHz can be removed. However, if the level of 1 kHz and that of 2 kHz are different in this case, the two levels are averaged or either of them is used. The obtained level is not equal to that of noise components, and a noise removal effect is reduced. If a speech signal to be recorded has a 1.5-kHz component, the component may attenuate to influence the speech quality. If the level changes over time, the canceling level needs to be adjusted again. If the spectrum of noise changes, it is difficult to cope with the change.